Abstract:

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Alumina matrix composite (AMC) has been widely used for artificial hip and knee joints
because of its phase stability in human body and its excellent wear resistance. The excellent
mechanical properties of strength and fracture toughness of zirconia materials are well known to be
closely related to stress-induced transformation from the tetragonal to the monoclinic phase, which
is accompanied with 4% volume increase of the zirconia crystal cell. However, it is also to be
considered that the material is prone to low temperature aging degradation (LTAD) under
hydrothermal environment, like in the human body. This LTAD is influenced by the tetragonal to
the monoclinic (t-m) phase transformation. T-m transformation also induces the formation of
microcracks at the material surface, and an increase in surface. Microcracking leads to a decrease of
mechanical properties, and could explain the failure of implants after some years in vivo [1, 2]
.Therefore, it is very important to study how to prevent phase transformation in zirconia
components. Transformed monoclinic zirconia percentage can be experimentally measured by
Raman spectroscopy and the residual stress distribution, which is related to phase transformation,
can be determined by a non-destructive piezo-spectroscopic analysis. In this paper, we attempted to
evaluate it from both stress and mechanical properties points of view by confocal Raman and
fluorescence spectroscopy.

Abstract: Electroless plating is one method to coat Al2O3 particles reinforced. This process has been carried out to coat Al2O3 with electrolite solution which content of nitride acid (HNO3), Al and Mg powders. The metal oxide layer of spinel phase (MgAl2O4) is formed on the surface of Al2O3 which can improve wettability of Al2O3. The addition of Mg powder into solution was various from 0.002 to 0.012 mol while Al powder was kept constant i,e. 0.018 mol. The effect of Mg on formation of metal oxide layer on Al2O3 particles have been studied. It is found that the addition of 0.004 mol of Mg generated homogeneous thin spinel layer (MgAl2O4) on the surface of Al2O3 particles. This condition was applied to form spinel layer on Al2O3 particles reinforced for making Aluminium Matrix Composites (AMC) with 12.5Vf% of Al2O3 particles reinforced. It is found that tensile strength and hardness as well as wear resistance of AMC has been improved compare to unreinforced.

Abstract: Aluminum matrix composites (AMCs) are characterized by improved mechanical properties in comparison to their unreinforced matrix alloys. But the knowledge about the fatigue behavior of AMCs in the HCF-and in the VHCF-regime is limited until now. Due to this AMC225xe and AMC xfine225 with an average SiC particle content of 25 vol.-% and particle sizes of 2.5 μm and 0.7 μm, respectively, as well as the base alloy AA2124 were fatigued up to 1010 cycles using the ultrasonic testing facility of the type "UltraFast-WKK-Kaiserslautern".To describe the fatigue behavior of the specimens several measuring devices were used to monitor and record the central process parameters. A very sensitive value to detect specimen failure at an early stage is the dissipated energy which can be determined as the integral of the generator power depending on the ultrasonic pulse time.In comparison to AA2124 the investigated AMCs have shown a considerably enhanced fatigue performance for stress amplitudes higher than 140 MPa. But below this stress amplitude for the matrix alloy run outs at 1010 cycles were realized whereas the AMCs failed at lower number of cycles still at lower stress amplitudes. Moreover, while crack initiation of the matrix alloy in all cases started at the surface for the AMCs the crack initiation point changes from surface to subsurface for more than 107 cycles. The subsurface failures of the composites were caused by microstructural inhomogeneities which could be identified with EDX and micro-CT as particle clusters and copper-iron-rich inclusions.

Abstract: Metal Matrix Composites possesses high mechanical properties compared to unreinforced materials. Aluminium Matrix Composites (AMC) is attracted in the emerging world because of its low cost, less weight and enhanced mechanical properties. In the present study the enhancement in mechanical properties like hardness and tensile strength of AMCs by reinforcing AA 6061 matrix with silicon carbide (SiC) and boron carbide (B4C) particles are analyzed. By enhanced stir casting method aluminium matrix was reinforced with boron carbide particulates and silicon carbide particulates with the various weight percentage of 2.5 %,5% and 7.5%.The tensile strength and hardness was found to increase with the increase in wt% of the reinforcement. From the analysis it is observed that the mechanical property of B4C reinforced AMC is significantly good compared to SiC reinforced AMC.